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https://issues.apache.org/jira/browse/HBASE-3171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13576045#comment-13576045
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Elliott Clark commented on HBASE-3171:
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Minor stuff to remove:
* Can remove the constants for ROOT from HConstants.
* Root's HRegionInfo can be removed.
* Root's HTableDescriptor can be removed.
* MetaMigrationConvertingToPB still has a bunch of Root related stuff.
* The region list template still explains what root is for.
Getting into the code now. Looks good.
> Drop ROOT and instead store META location(s) directly in ZooKeeper
> ------------------------------------------------------------------
>
> Key: HBASE-3171
> URL: https://issues.apache.org/jira/browse/HBASE-3171
> Project: HBase
> Issue Type: Improvement
> Components: Client, master, regionserver, Zookeeper
> Reporter: Jonathan Gray
> Attachments: HBASE-3171.patch, HBASE-3171-v2.patch,
> HBASE-3171-v3.patch, HBASE-3171-v4.patch
>
>
> Rather than storing the ROOT region location in ZooKeeper, going to ROOT, and
> reading the META location, we should just store the META location directly in
> ZooKeeper.
> The purpose of the root region from the bigtable paper was to support
> multiple meta regions. Currently, we explicitly only support a single meta
> region, so the translation from our current code of a single root location to
> a single meta location will be very simple. Long-term, it seems reasonable
> that we could store several meta region locations in ZK. There's been some
> discussion in HBASE-1755 about actually moving META into ZK, but I think this
> jira is a good step towards taking some of the complexity out of how we have
> to deal with catalog tables everywhere.
> As-is, a new client already requires ZK to get the root location, so this
> would not change those requirements in any way.
> The primary motivation for this is to simplify things like CatalogTracker.
> The way we can handle root in that class is really simple but the tracking of
> meta is difficulty and a bit hacky. This hack on tracking of the meta
> location is what caused one of the bugs over in HBASE-3159.
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